The invention relates to an air-guiding system between compressor and turbine of a gas turbine engine operated with a high pressure ratio.
The performance of gas turbine engines can be improved, among other measures, by increasing the pressure ratio. Connected therewith are however, on the one hand, higher axial forces acting on the shaft bearing, said forces having to be compensated, and on the other hand there is a distinct temperature increase and a correspondingly high thermal stress of the components adjoined downstream to the compressor, in particular, of the compressor shaft cone and the inner casing of the combustion chamber enclosing the latter. Because of extensive vorticity zones between stationary casing and rotating shaft and the friction losses resulting therefrom, there is a further temperature increase of the air and consequently an increased thermal stress of the shaft portion between compressor and turbine and of the inner casing of the combustion chamber enclosing the latter. Furthermore, by the vortex structures, flowing-off of the air from the chamber is made difficult, and thus the air temperature and the thermal stress of the material are further increased and the expected life of the respective components is reduced.
Due to the high thermal stress and the shorter life caused thereby it is necessary to use cost-intensive, high heat resistant materials for the respective components. On the other hand, due to the conditions existing in the chamber between the inner casing of the combustion chamber and the shaft and the temperature increase resulting therefrom, there is only available cooling air having an increased temperature for the subsequent cooling of the high-pressure turbine.
It is the object of the present invention to provide a gas turbine engine operated at an increased pressure ratio with simultaneous axial thrust compensation such that the thermal stress in the air chamber formed between the high-pressure shaft and the inner casing of the combustion chamber and loaded with a cooling air flow is low and therefore cost-effective materials can be used. It is another object to reduce the consumption of cooling air and to thereby increase the efficiency of the engine and lower the fuel consumption.